diff --git a/src/lerobot/processor/hil_processor.py b/src/lerobot/processor/hil_processor.py
index b271c560a..82bec9f9d 100644
--- a/src/lerobot/processor/hil_processor.py
+++ b/src/lerobot/processor/hil_processor.py
@@ -282,15 +282,16 @@ class RewardClassifierProcessor(ProcessorStep):
             self.reward_classifier.eval()
 
     def __call__(self, transition: EnvTransition) -> EnvTransition:
-        observation = transition.get(TransitionKey.OBSERVATION)
+        new_transition = transition.copy()
+        observation = new_transition.get(TransitionKey.OBSERVATION)
         if observation is None or self.reward_classifier is None:
-            return transition
+            return new_transition
 
         # Extract images from observation
         images = {key: value for key, value in observation.items() if "image" in key}
 
         if not images:
-            return transition
+            return new_transition
 
         # Run reward classifier
         start_time = time.perf_counter()
@@ -300,8 +301,8 @@ class RewardClassifierProcessor(ProcessorStep):
         classifier_frequency = 1 / (time.perf_counter() - start_time)
 
         # Calculate reward and termination
-        reward = transition.get(TransitionKey.REWARD, 0.0)
-        terminated = transition.get(TransitionKey.DONE, False)
+        reward = new_transition.get(TransitionKey.REWARD, 0.0)
+        terminated = new_transition.get(TransitionKey.DONE, False)
 
         if math.isclose(success, 1, abs_tol=1e-2):
             reward = self.success_reward
@@ -309,7 +310,6 @@ class RewardClassifierProcessor(ProcessorStep):
                 terminated = True
 
         # Update transition
-        new_transition = transition.copy()
         new_transition[TransitionKey.REWARD] = reward
         new_transition[TransitionKey.DONE] = terminated
 
diff --git a/src/lerobot/robots/so100_follower/robot_kinematic_processor.py b/src/lerobot/robots/so100_follower/robot_kinematic_processor.py
index 62cffc4d2..1a349d106 100644
--- a/src/lerobot/robots/so100_follower/robot_kinematic_processor.py
+++ b/src/lerobot/robots/so100_follower/robot_kinematic_processor.py
@@ -251,8 +251,9 @@ class InverseKinematicsEEToJoints(ProcessorStep):
     initial_guess_current_joints: bool = True
 
     def __call__(self, transition: EnvTransition) -> EnvTransition:
-        act = transition.get(TransitionKey.ACTION) or {}
-        comp = transition.get(TransitionKey.COMPLEMENTARY_DATA) or {}
+        new_transition = transition.copy()
+        act = new_transition.get(TransitionKey.ACTION) or {}
+        comp = new_transition.get(TransitionKey.COMPLEMENTARY_DATA) or {}
 
         x = act.get(f"{ACTION}.ee.x", None)
         y = act.get(f"{ACTION}.ee.y", None)
@@ -262,7 +263,7 @@ class InverseKinematicsEEToJoints(ProcessorStep):
         wz = act.get(f"{ACTION}.ee.wz", None)
 
         if None in (x, y, z, wx, wy, wz):
-            return transition
+            return new_transition
 
         # Get joint positions from complimentary data
         raw = comp.get("raw_joint_positions", None)
@@ -292,10 +293,10 @@ class InverseKinematicsEEToJoints(ProcessorStep):
                 new_act[f"{OBS_STATE}.gripper.pos"] = float(raw["gripper"])
             else:
                 new_act[f"{ACTION}.{name}.pos"] = float(q_target[i])
-        transition[TransitionKey.ACTION] = new_act
+        new_transition[TransitionKey.ACTION] = new_act
         if not self.initial_guess_current_joints:
-            transition[TransitionKey.COMPLEMENTARY_DATA]["reference_joint_positions"] = q_target
-        return transition
+            new_transition[TransitionKey.COMPLEMENTARY_DATA]["reference_joint_positions"] = q_target
+        return new_transition
 
     def transform_features(self, features: dict[str, PolicyFeature]) -> dict[str, PolicyFeature]:
         features[f"{OBS_STATE}.gripper.pos"] = (PolicyFeature(type=FeatureType.ACTION, shape=(1,)),)
@@ -333,18 +334,19 @@ class GripperVelocityToJoint(ProcessorStep):
     discrete_gripper: bool = False
 
     def __call__(self, transition: EnvTransition) -> EnvTransition:
-        obs = transition.get(TransitionKey.OBSERVATION) or {}
-        act = transition.get(TransitionKey.ACTION) or {}
-        comp = transition.get(TransitionKey.COMPLEMENTARY_DATA) or {}
+        new_transition = transition.copy()
+        obs = new_transition.get(TransitionKey.OBSERVATION) or {}
+        act = new_transition.get(TransitionKey.ACTION) or {}
+        comp = new_transition.get(TransitionKey.COMPLEMENTARY_DATA) or {}
 
         if f"{ACTION}.gripper" not in act:
-            return transition
+            return new_transition
 
         if "gripper" not in self.motor_names:
             new_act = dict(act)
             new_act.pop(f"{ACTION}.gripper", None)
-            transition[TransitionKey.ACTION] = new_act
-            return transition
+            new_transition[TransitionKey.ACTION] = new_act
+            return new_transition
 
         if self.discrete_gripper:
             # Discrete gripper actions are in [0, 1, 2]
@@ -367,11 +369,11 @@ class GripperVelocityToJoint(ProcessorStep):
         new_act = dict(act)
         new_act[f"{ACTION}.gripper.pos"] = gripper_pos
         new_act.pop(f"{ACTION}.gripper", None)
-        transition[TransitionKey.ACTION] = new_act
+        new_transition[TransitionKey.ACTION] = new_act
 
         obs[f"{OBS_STATE}.gripper.pos"] = curr_pos
-        transition[TransitionKey.OBSERVATION] = obs
-        return transition
+        new_transition[TransitionKey.OBSERVATION] = obs
+        return new_transition
 
     def transform_features(self, features: dict[str, PolicyFeature]) -> dict[str, PolicyFeature]:
         features.pop(f"{ACTION}.gripper", None)